More than 40 families from Nanacamilpa, a small town 45 miles east of smoggy Mexico City, in the Tlaxcala state, manage the forest and offer firefly walking tours, according to The Associated Press. Visitors descend on conifer forests like the Piedra Canteada reserve to catch the spectacle, in which bioluminescence meets romance.

After an agricultural price bust more than 15 years ago, the families tried to start a campground business, but struggled to draw customers. To get by, they had repeatedly surpassed government logging quotas, the AP reported.

So five years ago, they turned to the fireflies—millions of them—which show up between June and August each year. The locals designed tours around the insects’ nightly display. It worked.